The present invention relates to a novel antiparasitic composition comprising an effective amount of a) a Formula (1) compound, wherein R1a, R1b, R1c, R2, R3, R4, and n are as defined herein, stereoisomer thereof, or a pharmaceutical or veterinary acceptable salt thereof, b) a macrocyclic lactone or derivative thereof and c) optionally, at least one additional veterinary agent, and further comprising at least one veterinary or pharmaceutical acceptable carrier; and a method of treating an animal with a parasitic infection, by administering an effective amount of said composition to the animal in need thereof.